Avery and Stachowski's relationship was detailed prominently on Netflix's "Making a Murderer." The pair started dating after Avery was exonerated for a 1985 rape he did not commit in 2003. Two years later, Avery was arrested for the murder of the 25-year-old Halbach. Stachowski broke off their two-year relationship shortly before Avery's trial.

While she doesn't offer groundbreaking evidence that Avery committed Halbach's murder, she did reveal some surprising points documentary viewers had not previously known.

First, Stachowski said she was supposed to get out of prison the day Halbach was killed.

"The day [the murder] happened, Steven was supposed to pick me up to go an AODA class, a drinking class," she said. "But for some reason, which I still don't know, the jail wouldn't let me out. And if they would've let me out, she still would have been alive. Because I would have been there."

Stachowski talking to filmmakers about Avery in "Making a Murderer." Netflix

She also backtracked on a moment in the documentary where she defends Avery by saying that she was on the phone with him during the day of Halbach's murder and she didn't notice anything suspicious.

"I'm looking at the phone bill from October 31," Stachowski told filmmakers in "Making a Murderer." "I called Steven at 5:36 p.m. — supposedly when all this murder or whatever was supposedly happening. And we talked for 15 minutes, and the conversation was normal. He didn't sound rushed or like he was doing anything. And if he was in the middle of doing something, we wouldn't have talked for 15 minutes."

But in the HLN interview, Stachowski contradicted this statement.

"He did sound funny — I mean, he didn't sound rushed or whatever — but he did sound funny like he was lying or hiding something," she told Lance.

As for a possible motive for why Avery would have wanted to kill Halbach, Jodi points to his anger and misogyny after his original incarceration in the 1985 sexual assault of Penny Beerntsen, which Avery served 18 years for before he was exonerated by DNA evidence in 2003.

Steven Avery after he was exonerated in 2003. AP

"He told me once, excuse my language, 'All b------ owe him,'" she said. "Because of the one [woman] who sent him to prison the first time. We all owed him. And he could do whatever he wanted."

Ultimately, Stachowski said she was convinced Avery killed Halbach from the beginning.

"Something in my gut told me he's guilty," she told Lance.

A large portion of the 30-minute interview with HLN focused on Stachowski and Avery's relationship. Stachowski called Avery "abusive" and a "monster," detailing distressing incidents of domestic violence, including one time when he hit, choked, and dragged Stachowski out the door and into his car.